The present invention relates to a fully differential voltage-current converter.
Conventional voltage-current converters are considered basic functional blocks in the analog design of integrated and discrete circuits.
Converters of this kind currently convert a single-ended voltage, i.e., an unbalanced voltage, into a current.
An example of this is shown in FIG. 1, wherein the voltage V.sub.R in input to the inverting terminal of the operational amplifier 1 is converted into a current I.sub.R.
Since the operational amplifier 1 forces its noninverting input to be equal to its inverting input, i.e., to V.sub.R, a current I.sub.R equal to V.sub.R /R flows through the resistor R. This current must be supplied by the P-channel MOS transistor 2; therefore, if the MOS transistor 2 is equal to the P-channel MOS transistor 3, the current I.sub.R is mirrored in transistor 3, obtaining current conversion of the input voltage V.sub.R.
This type of voltage-to-current conversion is acceptable if the supply voltages are not particularly low and the required performance is not high.
Otherwise, the current trend is to use differential methods, which offer advantages in terms of immunity to supply noise, to noise produced by clock rejection and generally to common-mode noise on the voltages in input to the differential operational amplifier.